Method of offset printing or decorating an article with thermoplastic color

ABSTRACT

Articles are printed or decorated with thermoplastic color by an offset process, by melting the thermoplastic color in a screen, applying the melted thermoplastic color by the screen to a transfer member which is at a temperature below the melting temperature of the thermoplastic color, adhesively coating the surface of the article to be printed or decorated, and then transferring the color from the transfer member to the adhesively coated article surface.

United States Patent James Sept. 5, 1972 54 METHOD OF OFFSET PRINTING R 2,739,529 3/1956 Fernandez ..10-1/41 x DECORATING AN ARTICLE WITH 2,841,075 7/1958 Ryckman ..10l/4l THERMOPLASTIC COLOR 3,418,926 12/1968 Hakogi ..l0l/44 X 3 511 178 5/1970 Curtin ..101/450 Inventor: Davld Richard James, Coverts1de,

HaSfield, England 3,388,658 6/1968 Cummmgs ..10l/35 UX [73] Assignee: Murray Curvex Printing Limited, FOREIGN PATENTS OR APPLICATIONS Gloucester, England 748,362 5/1956 Great Britain ..101/35 22 Filed; 25, 1970 736,312 9/1955 Great Britain ..101/35 1 App]' 13387 Primary Examiner-Robert E. Pulfrey [30] Foreign Application Priority Data Assistant ExaminerClifford D. Crowder Feb. 25, 1969 Great Britain ..1 0,0015/69 521 US. Cl. ..-......101/211, 101/44, 101/426 1 A R [51] Int. Cl ..B4lt 17/00, B4lm l/14 Articles are I printed or decorated with thermoplasuc [58] Field of Search ..101/35-, 41-44, 6010, by an Offset process, by melting the the 1010113426 moplastic color in a screen, applying the melted thermoplastic color by the screen to a transfer member [56] References cued which is at a temperature below the melting tempera- UNITED STATES PATENTS ture of the thermoplastic color, adhesiyely coating the surface of the artlcle to be printed or decorated, and Fernandez then the olor from the transfer member Conkle to the adhesively coated article urface 3,276,358 /1966 Lusher ..101/35 X 1 2,776,509 l/l957 Kienel ..101/35 X 5 Claims, 2 Drawing Figures 2,842,046 7/1958 Murray ..'...101/41 2,940,864 6/ 1960 Watson ..1 17/ 17.5

A 3; 32 fit 33 13 33m 26 Q I I i I l P'A'TENTED m 3.688.695

' sum 2 or 2 INVENTOR Dawn A M/10x0 Jana:

METHOD OF OFFSET PRINTING R DECORATING AN ARTICLE WITH THERMOPLASTIC COLOR This invention relates to the offset printing or decorating of articles. Although the invention is mainly of application to the pottery industry it can also be used for printing contoured and flat articles generally.

The object of the invention is to provide a method which although applicable to single-color printing is of particular advantage with multi-color printing in that the complete colored decoration or pattern can be applied to the article at a single impression. The invention enables articles to be so decorated on a surface which is irregular, rough or generally possesses a three-dimensional character, and a further object is to provide such method which can very satisfactorily be adapted to semi-automatic and automatic procedures.

It is known to effect single-color printing or decorating of articles with the color transferred from an intaglio plate to the article utilizing as a transfer member a resilient pad, which spreads over the plate to extract the color therefrom and similarly spreads over the surface of the article to develop the design thereon. It has been proposed that the transfer member should alternatively be an elastic membrane which is inked using a screen stencil, the resilient pad being retained and used to press the elastic membrane .against the article. The present invention is advantageously employed with such an arrangement for multi-color printing at a single impression, although the scope of the invention is by no means so limited. For example, the method of the invention can be employed in a process of hand decoration, an intermediate product then being a transferable print which is applicable by hand.

The problem of providing a transfer member which will conform intimately with an irregular surface has already been solved, but for multi-color printing by a single impression to be effected on an economic basis it is necessary for a number of additional problems to be solved. One such problem is to ensure that at the instant of offset of the image from the transfer member to the article the entire image, or at least'a high percentage of the color forming the image, is actually offset on.

to the article; another is that a multiplicity of colored images in perfect registration one with another must be laid upon the transfer member in rapid succession, and this in turn necessitates that the individual color images must be rapidly rendered dry to the touch so that the application of successive colored images to the transfer member will not smudge or otherwise spoil images previously applied and that suitable means must be employed for applying color to the transfer member in a predetermined pattern. The present invention provides solutions to these problems.

According to the invention a method of printing or decorating an article comprises the steps of applying a thermo-plastic color with a melt temperature above ambient temperature to a heated stencil screen, maintaining thecolor molten in the screen and transferring it by contact to a transfer member which is cold, i.e. below the freeze temperature 'of the color, and offsetting the color from the transfer member to a surface of the article.

The stencil is preferably a screen and desirably a screen of metal mesh of stainless steel or bronze, and the color may have a melt point of about 55 to 60 C.

and comprise an inorganic pigment in a wax base. When the molten color in the heated screen is brought into contact with the cool transfer member this causes the color to freeze and dry instantaneously, so that there is no offset on to the back of subsequent screens utilized to apply successive images of different colors.

It will be appreciated that as many colored images as are necessary to produce the complete color pattern can be successively applied to and frozen on to the transfer member before the image is offset on to the article. Two alternative ways of achieving offset of the image on to the article may be employed. According to the first of these the article surface is first sized with an adhesive which provides a high surface affinity for the frozen image, which affinity materially exceeds the affinity of the colors for the surface of the transfer member which is raised to a critical temperature slightly below the melt point of the color. At this temperature the wax base of the color will deform, stretch or compress without cracking. According to the other way, the transfer member is heated, prior to offsetting, to a temperature exceeding the melt point of the thermo-plastic color, and momentarily pressed into intimate contact with the cold surface of the article. Thus the image first wets then freezes to the cool article, and since the transfer member is relatively hot there still exists a fine liquid interface between the color frozen on the cold article and the still hot transfer member. Thus clean separation of the transfer member from the article is ensured, with only a very small and tolerable amount of color left on the surface of the transfer member.

However offsetting onto the article is achieved it is clearly normally desirable that the transfer member surface should have a low affinity for the color, and in this respect a silicone rubber or silicone treated surface has been found satisfactory. Thus when the transfer member is an elastomeric membrane, it is preferably of silicone rubber or rubber which is silicone faced on its operative surface.

In the case of transferable prints applicable to the surface of the article by hand, the transfer member may be any flexible material such as paper, plastic or rubber sheeting having a surface which is non-porous and possesses low surface affinity for the thermo-plastic color.

A machine employing the method of the invention is illustrated in the accompanying drawings and will now be described by way of example. In the drawings:

FIG. 1 is a somewhat diagrammatic elevational view of the machine forming the embodiment, and

FIG. 2 is a plan view thereof.

The machine comprises two separate sections 1 and 2 which have independently mounted base stands 3 and 4. The two stands support rotary tables, 5 and 6 respectively, which are indexed sequentially and in synchronism. Either automatic or semi-automatic indexing means, which are not illustrated, are provided for'the two tables 5 and 6, these means being interlocked to synchronize the indexing movements. The machine illustrated is for two-color decoration of articles of pottery, but by increasing the number of stations on the table 5 any number of colors can be applied at each offsetting operation.

Four stations A, B, C and D are provided for the machine section 1, the table 5 of which indexes in the direction of the arrow 7. The table 6 is shown as indexing in the same rotary direction, illustrated by the arrow 8. At the stations A and B two metal mesh stencil screens 9 and 10 are arranged. These do not rotate with the table and are supported from an upstanding stationary column 12 of the section 1. Four similar transfer members 13, each in the form of an elastomeric silicone rubber membrane stretched over an open frame, are respectively mounted on the table 5 so as to index therewith. The membranes are attached to the frames around a circular periphery so as to undergo uniform radial deformation during the offsetting operation. At each station a circular support platen or bolster" 14 is fixed to the table 5 to support the membrane of the corresponding transfer member 13 while color is applied thereto from the screens 9 and 10, which screens are respectively supplied with the two colors.

Cooling water circulates through the bolsters 14, the upper surfaces of which are perforated to enable a vacuum to be applied to hold down the transfer membranes at the stations A and B while color is applied. This produces intimate contact between the membrane and the bolsters 14 at these stations, with consequent cooling of the membrane below the freeze temperature of the thermo-plastic color. The vacuum also serves to lock the membrane to the rigid bolster so preventing the slightest-movement of the membrane whilst subjected to the indirect action of the squeegee, thus preventing print deformation. Radiant heaters 15 and 16 are respectively mounted above the screens 9 and 10, and these serve to maintain the color in these screens molten until it is applied to and freezes on a cold transfer membrane. The heaters 15 and 16 are suspended from radial arms 17 and 18 which project from the top of the stationary column 12. The screens 9 and are respectively provided with squeegees l9 and 20 for spreading the corresponding thermo-plastic colors, and the heaters and 16 serve to heat these squeegees and the supply of color at each screen. Pneumatic or hydraulic cylinders 22 and 23 respectively stroke the squeegees over the screens 9 and 10, these cylinders being operated in sequence with indexing movement of the table 5. The screens are preferably worked off contact" with the membrane to ensure minimum heat flow between screen and membrane, being positioned at a height which may also provide a vertical clearance to allow the transfer members 13 to pass below them as the table 5 indexes. For clarity the heaters 15 and 16 and their supporting arms 17 and 18 are omitted from FIG. 2.

Thus, after color has been applied to a transfer member 13 at station A it is indexed to station B where the other color is applied, at the same time the first color being applied to the next following transfer member 13 which is now at station A. After both colors have been applied a transfer member 13 indexes to station C and it is there heated to a critical temperature to facilitate offsetting, each transfer member being inverted as it passes from station B to station C. Thus it reaches station C in the inverted position shown in broken lines in FIG. 2, and to allow inversion each transfer member frame is hinged at its outer edge 24. When at the station C an inverted transfer member 13 is positioned under a radiant heater 25 which heats the applied color pattern through from the underside of the membrane, heating to thecritical temperature preventing cracking or crazing" of the color as it is offset.

The table 6 has eight stations at each of which an article support pad 26 is fixed to the table, including an offsetting station E preceded by heating and adhesive applying stations F and G. A radiant heater adhesive drier 27 and an adhesive applicator head 28 are respectively mounted on radial arms 29 and 30 projecting from a stationary column 31,- and these arms can be swung about the column 31 so that the actual stations F and G can be chosen to suit the adhesive characteristics. In FIG. 2 the intermediate idle stations are identified as H, and fresh articles can be loaded at station Ha and the decorated articles unloaded at station Hb, for example, with the set-up illustrated. If the machine is to be loaded with articles pre-coated with adhesive, the heater at station F which serves to dry the adhesive need not be used nor, of course, the applicator head 28, The latter operates in sequence with indexing movement of the table and discharges the adhesive through'a spray nozzle 32 on to thearticle 33 at the station G. Each support pad 26, which may be resilient, may incorporate vacuum holding means by which the supported articles 33 are firmly held down in the correct position for offsetting. For clarity the support pads are omitted from the stations H in FIG. 2. i

The tables 5 and 6 are disposed side by side, and a transfer member 13 inverted at station D overlies the article 33 at station E, with the color pattern now on the lower side of the transfer membrane and hence facing the article. It is offset onto that article by means of a power-actuated pressing head 34 fixed to the column 31 at station E. The head 34 comprises a deformable convex pad of gelatine 35 by which the inverted membrane is pressed intimately into contact with the upper article surface to be decorated. This pad 35 is movable between limits by a pneumatic or hydraulic cylinder 36. Substantially complete offsetting results from the preheating of the color pattern at station C and the pre-- coating of the article by adhesive at station G,'which adhesive has dried to a tacky condition as a result of air drying and the heating at station F.

Instead of completely inverting the transfer members 13 at the heating station C ready for indexing to station D, as has been described, the transfer members 13 may alternatively merely be lifted slightly at station C so that they are out of contact with the cooled bolster 14 at that station. This requires suitable re-positioning of the heater 25 and also inversion of the transfer members 13 as they pass from station C to station D.

It will be appreciated that the rotary table arrangement of station 1 could, if desired, be replaced by a linear conveyor arrangement advanced in a stepwise manner beneath the presser head at the offsetting station. The adhesive applicator and drying heater if required would be suitably positioned along the conveyor ahead of the ofi'setting station.

I claim:

1. A method of printing or decorating an article,

comprising the steps of applying to a heated stencil screen a thermoplastic color with a melting temperature above ambient temperature, maintaining the color 4. A method according to claim 1, wherein a multicolor pattern is offset on to the article surface, includ- 7 ing the steps of applying the individual color images silicone treated surface which provides a low affinity for the color.

3. A method according to claim 1, using for the transfer member an elastomeric membrane.

successively to the transfer member, allowing each such image to freeze thereon before the next is applied, and subsequently offsetting the complete pattern on to the article.

5. A method according to claim 1 wherein the offsetting is achieved by hand with the transfer member and the applied color in the form of a transfer, the

transfer member being a sheet of flexible material to which the color is transferred from the heated screen and which has a surface which is non-porous and possesses low surface affinity for the thermo-plastic color.

* i i l l 

1. A method of printing or decorating an article, comprising the steps of applying to a heated stencil screen a thermoplastic color with a melting temperature above ambient temperature, maintaining the color molten in the screen, transferring the color by contact to a transfer member which is at a temperature below said melting temperature of the color, coating that surface of the article which is to be printed or decorated with an adhesive so that the surface affinity of the color is greater for the coated surface of the article than for the surface of the transfer member, pressing together the color-coated surface of the transfer member and the adhesive-coated surface of the article, and separating the transfer member and the article whereby the color offsets from the transfer member to the coated surface of the article.
 2. A method according to claim 1, using as the transfer member a member having a silicone rubber or silicone treated surface which provides a low affinity for the color.
 3. A method according to claim 1, using for the transfer member an elastomeric membrane.
 4. A method according to claim 1, wherein a multi-color pattern is offset on to the article surfAce, including the steps of applying the individual color images successively to the transfer member, allowing each such image to freeze thereon before the next is applied, and subsequently offsetting the complete pattern on to the article.
 5. A method according to claim 1 wherein the offsetting is achieved by hand with the transfer member and the applied color in the form of a transfer, the transfer member being a sheet of flexible material to which the color is transferred from the heated screen and which has a surface which is non-porous and possesses low surface affinity for the thermo-plastic color. 